Alzheimer?s disease (AD) is a devastating neurodegenerative dementia associated with A? and Tau pathologies in brain that currently afflicts 5.4 million individuals in the USA. The major hypothesis of AD is the A?/amyloid hypothesis, which states that the accumulation of A? is an early and necessary event in the pathogenic progression that promotes tauopathy, mitochondrial & synaptic dysfunction, and neuroinflammation, leading to synaptic and neuronal loss. Emerging evidence indicates that the release and uptake of extracellular vesicles (EVs) from one cell to another represent an important form of intercellular communication that could transmit beneficial or pathogenic signals across different cells. Our preliminary data indicate that A?42 oligomers and mutant Tau dramatically alter the release of EVs (exosomes & microvesicles). Despite these significant changes, the specific changes in the EV proteome and the interactive and directional effects between specific neuronal compartments and microglia are unknown. Moreover, given that EVs are abundant in biological fluids such as plasma, alterations in the proteome of brain-derived EVs provides the unique opportunity to develop novel biomarkers from blood plasma. Our working hypothesis is that AD pathological drivers significantly alter the EV proteome (exosomes & MVs) as well as their pathogenicity via local and nonlocal mechanisms and that those changes in the EV proteome of brain will serve as useful pathology and disease-specific biomarkers in blood plasma. In this proposal, we will 1) profile and validate the changes in proteome of EVs from neuron/microglia cultures in response to AD pathogenic drivers and 2) determine the local and directional pathogenicity of A?42 treatment-derived exosomes isolated from the interactive milieu of neurons and microglia. Therefore, the results of these studies will provide critical insights to the interactive and directional effects of A?42, Tau, and microglia in the release of EVs and EV proteins as well as their pathogenicity, while identifying the major changes in the EV proteome in the AD pathogenic setting. Such information collectively will aid in the identification of EV-based biomarkers for AD and establish a platform for extensive functional characterization of pathologically-derived EVs and their proteome content.